Radio transmitter apparatus



J. EVANS 0 RADI TRANSMITTER APPARATUS 2 Sheets-Sheet 1 Filed Nov. 50,1954 Llll'l /u HW F lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll lll ll Jul 13,1937.

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July 13, 1937. J. EVANS 2,086,905

I RADIO TRANSMITTER APPARATUS Filed Nov. 50, 1934 2 Sheets-Sheet 2GRID/31198 lllvoos FOTENTl/IL FOTENT/fiL POTENTIflL BE/06E 37 67 7BRIDGE INVENTOB:

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Patented- July is, 1937' PATENT OFFICE I RADIO TRANSMITTER APPARATUSJohn Evans, Riverside, N. J., assignor, by 'mesne assignments, to RadioCorporation of America, New York, N. Y., a corporation of DelawareApplication November 30, 1934, Serial No. 755,393

This invention relates to high frequency radio transmitting systems andmore particularly to apparatus having an improved form of constructionforv supporting and interconnecting high power electron discharge tubes.

I have found that ultra-short waves, say of the order of 30 to 80megacycles, may be generated and amplified by means of electrondischarge tubes having water cooled anodes. The ultra high frequencyenergy thus produced can be utilized under optimum conditions ofefficiency, provided proper precautions are taken to obtain resonantcircuits between stages and to so dispose these circuits that they shallbe properly shielded at the same time'that they are. suitablycoordinated in length withrespect to the ope'rating wave length.

Accordingly, it is among .the objects of my invention to provideapparatus of the character above suggested in which electricalconnections 7 between stages of electron discharge tube networks aremade adjustable to resonant conditions at the same time that they areproperly shielded and insulated.

A further object is to provide a supporting pedestal for an electrondischarge tube .inwhich may be disposed any desired portion-of an anodecooling system.

Anotherobject of my invention is to so arrange the output circuits froma pair of water cooled thermionic tubes that such tubes may be suitablyoperated in a push-pull manner and with a maximum efliciency of outputenergy.'

Another object is to provide hollow pedestals for tuning and shieldingpurposes whereby the necessary interconnecting circuits betweensuccessive stages of push-pull operated tubes may be obtained, whileavoiding some of the serious energy losses which were heretoforeinherent in the conventionalmeans for insulating and shielding suchcircuits.

Another object of my invention is to provide convenient adjusting meansfor obtaining the necessary electrical lengths of the conductors whichare used between two anodes of a pushpull pair of electron dischargetubes and to provide further length-adjusting means for the 0on ductorsconstituting an output circuit for such tubes. 3

' Among the advantageous features of my invention the following may bementioned,(1) a tuned circuit isprovided which has an extremely highpower factor; (2)'-the dissipation of high frequency energy by creepageover ceramic or other conventional insulators is voided; (3)

radiation losses in the network are made negligible by suitableshielding; (4) inductances and capacitances are efliciently distributedinstead of being lumped, thereby avoiding over-heating of theconductors; and (5) a wide range of operating frequencies may be hadwithout departing from an optimum ratio of inductance to capacitance ofthe network.

The foregoing and other objects and advantages of my invention will bemore clearly understood upon reference to the following detaileddescription when taken in connection with the accompanying drawings, inwhich Figure 1 is a view, partly in se tion and somewhat fragmentary, oftwo pedestals which are adapted for supporting high power electrondischarge tubes;

Fig. 2 is a diagram which is referred to in the specification forexplaining the theory of operation of my invention; and Fig. 3 is stillanother diagram presenting more or less in plan view the arrangement ofsix pedestals which may be suitably assembled with apparatus forobtaining the necessary tuning adjustments as between stages of twopairs of electron discharge tubes operated in a push-pull manner. I

Some ofthe mechanical details of the apparatus herein disclosedcorrespond closely'to those which have been described ,in my Patent No.2,051,520, August 18, 1935, and assigned to the assignee of the instantapplication. In that application there was-disclosed a system of pillarshaving internally disposed conductors and a bridging memberwhich couldbe adjusted upf wardly and downwardly in order to obtain a opening I ismade between the stand pipe and p j the cooling chamber for admittancepf a cool ing fluid such as water. An intake pipe 9 serves toestablishconnections between any suitable source of cooling fluid and theinterior of the stand-pipe 5. An outlet pipe ii is disposed with in thestand-pipe and runs the full length thereof for carrying away the waterwhich has ab- Any suitable clamping device such as the ring l5 may beprovided for holding the electron discharge tube in position and forsealing the anode withinthe cooling chamber. Surrounding the stand-pipe5 is a shielding member I! made of metal and having a base l9 formed ofany suitable material. The base is supported by insulators 2|. The topend of the tubular shield I1 is rolled over as shown at 23 in order tolize a bridging member 25, the height of which is determined undercontrol of a threaded rod 21, which, in turn, is vertically disposedmid-way betweentwo of the pedestals. The bridging member 25 extendsthrough slots 25 in the shields I1 and has suitably mounted at each enda set of resilient brushes 29. Certain of these brushes bear against theouter wall of each stand-pipe 5,

, while others of the brushes bear against the inner wall of eachshielding column IT.

The lead screw. 21 is preferably supported at the bottom thereof by athrust bearing 3| and at the top by an ordinary bearing 33. The bearings3| and 33 are supported. on insulators 35, these insulators beingattached in any suitable manner skin effect at the frequencies for whichmy ing member II.

to the shielding members I'I.

Upward and downward adjustment of the v bridging member .25 is obtainedby means of a crank 31 the shaft of which carries a bevel gear 39meshing with a bevel pinion 4|. The pinion 4| is carried on a shaft 43which is socketed in an insulating member 45. The lead screw 21 is alsosocketed in this insulating member 45. The metallic parts of the crankand transmission members are thus insulated from the lead screw 21.

In the operation of the device shown in Fig. 1, assuming that twoelectron discharge tubes are mounted onthe pedestals for a push-pullstage of oscillation generation or amplification, the bridging member 25will be so adjusted that standing waves will be formed between theanodes of the two tubes. High frequency currents traverse the upperportions of the stand-pipes 5, also the brushes 23 and the shieldingmembers l1. At the center of ,the bridge 25 a node of energy is alsodeveloped. The high frequency energy which traverses the, interior wallsof the shielding members I! above the bridging member reacts bothinductively and capacitively upon the opposing walls of the stand-pipes5. This inductance and capacitance constitute an essential part of thetuned circuit; while the bridging member and the other elements whichconductively interconnect the anodes of the two tubes form abalancingcircuit having a nodal point at its center of symmetry, whichis also the center of the bridging member25. Below the bridging.mem-

her there is substantially no leakage of high frequency currents.Furthermore, the so-calledapparatus is intended to be worked is so greatthat substantially no high frequency currents are'developed on theexterior walls of the shield- In order to supply suitable anodepotentials to the electron discharge tubes which are sup-. ported by mypedestals,- as shown in Fig. 1, any

sorbed heat from the anode. of the radio tube.

This pipe H terminates at the top in a receptacle l3 for the anode.

suitable connection (not shown) may be made at the bottom of eachstand-pipe, say by strapping a conductor to the intake pipe 3. Usually,

be satisfactorily tuned. In this diagram there appear two electrondischarge tubes 41 constituting a first stage, and two more tubes'49constituting a second stage. These tubes are somewhat conventionallyrepresented as having each acathode 5|, a grid 53 and an anode 55. As isusual in high power transmission networks, the anode 55 extendsoutwardly from the glass envelope of the vacuum tube in order that itmay be properly cooled in a water jacket. The tubes 41 are indicated asmounted upon two of the pedestals such as those shown in Fig. 1. In thiscase, however, a modification is -made in the pedestals in that, inaddition to the bridging member 25, individual conductors 51 areprovided having brushes thereon which contact only with the'stand-pipes5. Slotted openings are made in the shielding members I! as shown at 59(Fig. 3). The metal of the shielding member isrolled back so as toeliminate the, possibility of corona discharge across the gap in whichthe conductor 51 is positioned.

In an embodiment of my invention which has beenbuilt, I have made theshield I! with a longitudinal opening 53 approximately one inch across.The conductor 51 is about one-fourth of an inch in thickness so that anair gap of threeeighths of an inch is maintained on either side of theconductor where it emerges from the inte- 65 which may be raised orlowered at will.

It is desirable to tune the circuit connections between stages. For thispurpose a lead screw 61 is provided in cooperation with the support 65.A crank withtransniission gearing similar to that shown in Fig. 1 isalso supplied,'controlling the upward and downward movement of thesupport 65 through the rotation of the lead screw 61. Details of thisstructure have not been shown because they may be well understoodfromthe showing of the crank and gearing in Fig. 1. It

will be seen, however,-that the two condensers 63, as well as theconductors connecting their opposing plates, are all supported throughinsulating means on one carrier 65, so that they can be raised andlowered together. Brushes 69, mounted on the conductors 51, engage withthe stand pipes 5 at some suitable elevation for taking ofi outputenergy from the discharge tubes 41. This energy is transmitted throughthe con- 7 densers 63 and thence through the conductors H II to otherbrushes [3 .which contact with tubular posts within the next pair "ofpedestals. From the tops of these posts. short flexible leads arecarried to the grids 50 of the tubes 49 respectively. By virtue of theadjustability of the elevation of the condensers 63 and bridgingconductors 51' and II it is possible to provide optior to' an antennasystem.

'I have found that in the operation of the ap- ,paratus', as hereinshown and described, nu-

of service. J 40 merous advantages are to be derived from the preferredstructural arrangements. For example, when operating such a system toproduce and transmit oscillations of a frequency of upwards of tenmegacycles, and where it is desirable to apply some thousands of voltsas direct current anode potential, this voltage is very satisfactorilyisolated from ground and at the same time the high frequency energy isalso kept within bounds. My apparatus isso designed that no radiofrequency voltages are developed in the region of the intake and outlethose connections of thecooling system. Prior to the development of myinvention, considerable trouble was experienced because of electrolysistaking place at the rubber hose connections. The rubber itselfwasactually disintegrated after a comparatively short term Since in myapparatus no high frequency energy is dissipated below the bridging.member 25, ,no such electrolysis can take place at the bottom of thestand-pipe, or at the hose connections. So-far as high frequencies areconcerned, the base of the stand-pipe and the base oi 1 the shieldingmember [-1 are both non-conductors. The twotubes 41 being worked inphase opposi- .tion to one another. develop currents which must ofnecessity neutralize each other across the bridge 25,- provided. thisbridge is adjusted to the proper level.

Many other advantages result from. the car I ryingout or my invention inthe mannerherein taught; Although I have shown a certain specificembodiment and have illustrated my invention in itsapplic'ation totransmitters having push-pull operated electron tubes, it is to beunderstood that many modifications may be made therein without departingirom the spirit and scope of the invention. I do not intend, therefore,to bev limitedexcept in-so-far as is necessitated by the prior artand bythe spirit of the appended claims. I claim. as my invention:

1. In a device of the class described, in combination, a pair ofelectron discharge tubes having fluid cooled anodes, a fluid chambersurrounding each of said anodes, tubular risers connecting with saidchambers for supplying a cooling fluid thereto, outlet pipescontainedwithin said risers,

pedestals are provided with insulating supports' 3. In a device of theclass described, in combination, pairs of electron discharge tubes, eachof said tubes having a cathode, a grid, and a fluidcooled anode;shielding pedestals for said tubes; tunable circuits each comprising, atleast in part, a conductive stand-pipe shielded by said pedestal;

. and anogie circuit including connections from said anodes to saidstand-pipes; adjustable bridging means connecting said stand-pipes foradjusting said anode circuit in at least one pair of said dischargetubes to resonance; and means adjustable on said stand-pipes forcoupling portions of said anode circuits to the grids of another of saidpairs of discharge tubes whereby energy is transferred from the anodesof one of said pair of tubes to the grids of another of said pair oftubes.

4. In a device of the class described, incombination, a pair of electrondischarge tubes, each of said tubes having a cathode, a grid, and ananode; shielding pedestals for said tubes; a conductive stand-pipedisposed withineach ofsaidpedestals: a tunable anode circuit for saidpair of tubes comprising said stand-pipes, connections,

from the anodes of said pair of tubes to said stand-pipes, and bridgingmembers having resil-- ient brushes adapted to'slidably contact saidstand-pipesy the shielding portions of said pedestals beinglongitudinally slotted'to permit insertion therein of said bridgingmembers, and having the edges of said slots rolled into a bead forminimizing-corona effect; and means for establishing a high-frequencyconnection to the stand-pipes within said shielding, pedestals.

5. A device in accordance with claim 3 and having male and femalethreaded means-for so adjusting the positions of said bridging membersas to obtain conditions of resonance between the anodes 0! said tubes. a

6. A device in accordance with claim 4 and having male and femalethreadedmeans for so adjusting the positions of said bridging members asto obtain standing waves in said anodev circuit.

JOHN EVANS.

